Precision high signal-to-noise ratio data, obtained within 1 year period at the Effelsberg 100 m telescope and the NRAO 300 foot (91 m) and 140 foot (43 m) telescopes, are used to determine the effect of resolution on 21 cm parameters. By comparing observations made with different beam sizes, profile widths are shown to continue to increase outward to the limit of the data. Redshift is also shown to vary radially for galaxies with significant rotating disks, widths more than 100 km/s. Nuclei of such systems are significantly blueshifted compared to outlying material, an effect difficult to understand if galaxies are optically thin at 21 cm. Profile shapes change radially in accord with the radial redshift variation. Galaxies with profile widths less than 100 km/s show a completely different pattern with no detectable change of redshift with radius. Systematic errors between radio telescopes are found to be vanishingly small after correction for differing resolution. Residual random errors are well below 1 km/s for S/N over 10, which permits very precise comparisons.